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eigrp summarization problem

i have a router configured with manual summarization and automatic summarization is enable which one the router at the boundary will advertise both or the automatic please help

3 REPLIES

Re: eigrp summarization problem

Hi Friend,

In a normal scanrio if you are looking for both internal routes and external routes summarization you use manual summarization. Automatic summrization doesnot summarize external routes. If you are using maunal summarization for external routes only then both the routes will be advertise otherwise maunal summarized routes will be advertised.

Manual summarization can be configured in EIGRP instead of automatic summarization by configuring a summary aggregate address for a

specified interface. This is useful if the summary route is sent only out of certain interfaces, but more specific routes are advertised over other interfaces. Manual summarization allows you to summarize routes at any bit boundary, but automatic summarization always summarizes at the major network boundary

When summarizing external routes in EIGRP using this method, the summary route becomes an internal route. Also, manual summarization can be configured on a specific interface belonging to the same major network as the specific routes being summarized, which is not possible using automatic summarization. For example, an interface belonging to 10.1.1.0/24 can be configured to summarize specific networks belonging to the major network 10.0.0.0/8.

HTH,

-amit singh

Re: eigrp summarization problem

Hi. It depends how you configure your summary. The auto summary will only summarise on class boundaries. If your manual summary is also on a class boundry then you will just see one summary advertised and it will be an EIGRP route (so you can't tell if it is an auto summary or manual - see below). This does not change if I use auto summary of manual. The summary route is the same.

D 30.0.0.0/8 [90/2297856] via 1.1.1.1, 00:00:01, Serial0/0.31

If I add a more spacific manual summary, say use a /16 mask for the same network then both summaries are advertised.

D 30.30.0.0/16 [90/2297856] via 1.1.1.1, 00:00:01, Serial0/0.31

D 30.0.0.0/8 [90/2297856] via 1.1.1.1, 00:00:01, Serial0/0.31

New Member

Re: eigrp summarization problem

thank alot for your help but i want to tell you somthing

i have read that auto-summary in eigrp will supress the subnets of the summarized route so no subnet will be advertised from the same major classfull network so if have an auto-summary for 10.0.0.0/8 network and you have made a manual summary with ip eigrp AS network mask for example 10.1.0.0/16 then both route will be installed but according to the supress rule only the 10.0.0.0/8 will be advertised !!! what do you think?? refer to the attached file from a cisco eigrp book

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